1. Field of the Invention
The present invention relates generally to agricultural vehicles. More specifically, the present invention relates to an agricultural vehicle which is capable of traversing trough formations such as levees and the like.
2. Description of the Relevant Art
It is currently a common practice to spray rice fields using aircraft. In fact, virtually all chemical application on rice is carried out by aircraft. However, this practice suffers from a number of drawbacks. The technique tends to be expensive and suffers from target spray drift which tends to be a major source of environmental problems. Further, timely aerial application can be a problem because crop dusting type aircraft cannot operate in high winds. Additionally, it is difficult to spray irregularly-shaped fields.
Conventional ground application spray rigs encounter difficulties in crossing rice levees because essentially all conventional tractors, trucks, trailer sprayers, and self-propelled sprayers use high pressure tires. These tires exhibit little or no flexure and apply a high force per unit area pressure to the surface under the tire. This tends to crush and flatten freshly pulled or plowed levees and induces the need to manually repair, using a hand shovel or the like, the ruts created by the tires.
In addition to the damage to the levees, conventional spray equipment has also suffered from a relatively large amount of mechanical breakage due to the vertically-oriented jolting caused when a levee is traversed.
In an effort to overcome the above mentioned problems encountered with aircraft and conventional tractor type equipment, and to ensure that timely spraying of rice crops and the like could be assuredly carried out irrespective of the ground and wind conditions, the applicant developed an ATV (all terrain vehicle) sprayer which exhibits excellent floatation capability on extremely soft ground.
This arrangement (shown in FIG. 1) comprised an ATV prime mover and an ATV sprayer vehicle (trailer). Both the ATV prime mover and the trailer used very soft low pressure elastic tires which exhibit very high flexing and floatation capabilities. The low weight of the ATV prime mover and ATV sprayer vehicle (hereinafter ATV sprayer) produced a very low ground pressure and enabled the ATV prime mover and ATV sprayer to roll over extremely soft ground without leaving ruts. This arrangement worked very well on level land in corn, wheat and soybeans.
However, the ATV sprayer vehicle in this instance used a conventional tandem axle including a cross-beam bracing arrangement interconnecting the front and back axles and was arranged so that the front and rear axles were spaced equally on either side of the pivot or fulcrum point of the two axles. In other words, the front and rear axles were spaced in a fixed 1:1 relationship with respect to the point intermediate the two axles about which the vehicle tends to tilt.
However, several features of this design prevented the ATV sprayer from crossing levees. The first was that the 1:1 axle spacing did not allow the vehicle to readily ascend the uphill face of a levee. Moreover, once on top of the levee, the vehicle chassis tended to straddle the levee and bring about the situation wherein the cross-beams which interconnect the front and rear axles either cut into or dragged across the top of the levee. The damage which resulted from this cutting or dragging action often was so severe as to require someone to use a shovel to repair the levee.
Another acute problem that was encountered is illustrated in FIG. 1. As shown, after the prime mover 10, in this case a four wheel ATV, has crossed the levee or undulation 12, the rigid connection 14 between the ATV (prime mover) and the trailer (ATV sprayer) 16 tended to hold the trailer level; that is, prevent the trailer from assuming a posture conducive to uphill travel. Therefore, the leading wheels 20 were subjected to a force which tended to pull them "straight through" the levee 12 and result in the generation of a moment of force which was sufficient to lift the rear wheels 22 off the ground in the manner illustrated in FIG. 1, and cause the ATV sprayer 16 to teeter forward.
This collision-like encounter with the front or ascending wall 12a of the levee produced an impact which was undesirably imparted to the spraying apparatus 24 mounted on the trailer (ATV sprayer) 16 and generated sufficient resistance, as the front wheels 20 tended to sink into the relatively soft wall 12a, to keep the ATV sprayer 16 teetering and in some cases to cause the ATV prime mover 10 to lose traction.